1. Field of the Invention
The present invention relates to a hydrogen generator and to an internal combustion engine provided with a hydrogen generator.
2. Description of the Related Art
In a fuel cell or an engine etc. using hydrogen as fuel, it is necessary to feed hydrogen to the system. As the apparatus for feeding hydrogen, in addition to an apparatus reforming natural gas etc., an apparatus storing hydrogen in a tank, etc., an apparatus generating hydrogen using ammonia as a material is known. In such an apparatus, it is possible to store ammonia in a tank and raise the ammonia to a high temperature for cracking to generate hydrogen.
Japanese Patent Publication (A) No. 5-332152 discloses an ammonia combustion engine, able to burn ammonia gas to obtain a drive force, provided with an ammonia cracking reactor which uses the exhaust gas of the combustion chambers to crack the ammonia. The exhaust gas from the combustion chamber is used to heat a heat exchange pipe in the ammonia cracking reactor. It is disclosed that the ammonia gas led into the heat exchange pipe is cracked into hydrogen and nitrogen by an endothermic reaction absorbing the heat of the exhaust gas.
In a hydrogen generator raising ammonia to a high temperature to crack it and generate hydrogen, it is possible to arrange a cracking catalyst including catalyst particles for promoting cracking of the ammonia. By arranging the cracking catalyst, the cracking of the ammonia can be promoted, for example, it is possible to lower the temperature for cracking the ammonia.
The cracking reaction of ammonia is an endothermic reaction, so to enable the cracking catalyst to continue to crack the ammonia, the cracking catalyst has to be supplied with heat. In the ammonia combustion engine disclosed in Japanese Patent Publication (A) No. 5-332152, the heat of the exhaust gas discharged from the combustion chambers is utilized to crack the ammonia gas into hydrogen and nitrogen. In this regard, in a system which obtains the heat required for cracking ammonia from the exhaust gas, if the temperature of the exhaust gas is low, it may not be possible to supply sufficient heat to the cracking catalyst and therefore hydrogen may not be suitably generated.
For example, at the time of cold start of an internal combustion engine etc., raising the temperature of the exhaust gas ends up taking time, so suitable generation of hydrogen by the hydrogen generator may also take time. In the ammonia combustion engine disclosed in this publication, an auxiliary heater is arranged for heating the heat exchange pipe for cracking the ammonia. When the temperature of the exhaust gas is low, the auxiliary heater is used to heat the heat exchange pipe. However, if using an auxiliary heater to heat a cracking catalyst to a temperature where the cracking reaction of ammonia occurs or if using an auxiliary heater to supply heat for continuing the cracking of ammonia, a large electric power will be required. There is therefore the problem that a large electric power source will be required for feeding power to the auxiliary heater.
Further, in this ammonia combustion engine, a hydrogen storage device is arranged. However, there is the problem that if arranging a hydrogen storage device in the hydrogen generator, the hydrogen generator will become larger in size or will become more complicated. Furthermore, there is the problem that when the hydrogen stored in the hydrogen storage device ends up being consumed, hydrogen will no longer be able to be supplied.